1. Field of the Invention
This invention relates generally to a fuel system for diesel engines, and more particularly to a closed, vacuum, diesel-fuel system having a fuel-measuring flow-control valve and sensor device.
2. Description of the Prior Art
As is well known in the art, various problems and difficulties are being encountered in providing suitable means for controlling and recording the amount of diesel fuel being used during the operation of a diesel engine as well as providing a suitable means to prevent air bubbles from entering the fuel-flow system.
In many diesel-engine fuel systems fuel is pumped from the fuel tank and is forced under pressure to the fuel injectors. Since a continuous flow of fuel is pumped to the injectors, there must also be provided a return-flow line, which in the past usually returned the excess fuel back to the tank by using a gravity-flow system. Gravity return-flow systems create their own problems, one being that fuel can not be fed directly into the main flow line going to the engine. Such an arrangement would normally interrupt the main flow in several ways.
One inherent problem is that the unburned returning diesel fuel will generally accummulate air bubbles. Thus, past systems have, by necessity, returned the unburned overflow fuel directly back to the tank, so as to allow the air bubbles to be separated from the fuel before returning through the main flow line.
Still another problem with diesel-fuel systems is that the returning unburned fuel must be cooled prior to being injected into the engine, since hot fuel will cause the engine to malfunction or operate in an inefficient manner.
However, various fuel systems and related fuel-operating-and-metering components have been tried and are being employed in an attempt to overcome the above-mentioned problems. Some of these systems and devices can be found in the following United States patents.
Fuel System for Diesel Engines, U.S. Pat. No. 3,672,394, is designed for treating diesel fuel wherein a meter is used in the system having a by-pass provided around the meter which includes a single metering valve, so that the by-pass can be used when it is desired that the flow not be measured.
U.S. Pat. No. 3,750,463 is a fuel-measuring system that includes a fuel-mixing device which returns unburned fuel to the fuel supply. As stated, "A valve is included in the system which has two positions a first one of which provides normal flow of fuel to the fuel mixing device and a second one of which provides flow through the by-pass to measure the flow. The valve is operably connected to the emergency brake or a power take-off so that it is moved to its second position when the emergency brake or power take-off is activated."
A fuel-use-rate meter is disclosed in U.S. Pat. No. 3,805,602. This meter is designed to accurately measure volume or weight of fuel consumed by an engine per unit of time.
Another fuel system for diesel engines is disclosed in U.S. Pat. No. 3,816,263 and is designed for treating liquid which may comprise as one instance means for cooling liquid. It also includes a by-pass around a meter when it is desired that the flow not be measured.
U.S. Pat. No. 3,949,602 relates to a meter capable of accurately measuring volume or weight of fuel consumed by an engine per unit of time.
Even with the existing systems that are available, there are still inherent problems to be solved. There is a need for an accurate fuel measurement in diesel-fuel systems, since providing a meter in the outflow line from the fuel tank would not only measure the fuel to be burned by the engine, but would also include the fuel which is constantly being returned to the fuel tank that was not originally consumed.